In the prior art, radiation therapy is conducted by externally irradiating the relevant area (malignant tumor or the like) of a subject (patient) with radiation by using a radiation irradiating device called Linac (not shown) for example. With the radiation therapy, the area where the subject will be irradiated is planned in advance of the radiation therapy. In other words, the radiation area which is appropriate for the status (the condition of the diseased section) of the relevant region of the subject M is decided in advance. When the radiation is actually being carried out, only this radiation area is irradiated. In other words, if healthy area outside of the radiation area is irradiated, there will be damage to normal tissue, and conversely, if a part of the radiation area is not irradiated, the anticipated effect from radiation is not achieved. In order to have just enough radiation and not too much or too littler, there is a need to decide on the radiation area in advance.
For the planning of the radiation area, normally, as described below, a radiation therapy planning device that is separate from the radiation device is used. In other words, the design and planning of the radiation area is often conducted off line.
In the radiation therapy planning device of the prior art, as shown in FIG. 10, a X ray tube 51, which shines a cone-shaped X ray beam at subject M, and an image intensifier (I—I tube) 52, which is a X ray detector detecting the fluoroscopic image from subject M, are placed on a gantry 53 opposite each other with subject M placed in between. A bed device 55 with a table 54 on which subject M is placed is in front of gantry 53. Table 54 can be moved vertically (raised and lowered), as well as horizontally in the lengthwise direction (forward and back; the Z direction of the body axis of subject M) and in the crosswise direction (side to side; perpendicular to the Z direction of the body axis of subject M). With the X ray irradiation of subject M by X ray tube 51, a fluoroscopic detection signal is outputted from I—I tube 52. Based on the fluoroscopic detection signal, a radiation planning fluoroscopic image is shown on the screen of an image display monitor (not shown) of a later stage. In addition, a film shooting mechanism (not shown) which is installed underneath table 54 conducts X ray film photography.
When planning the radiation area using the radiation therapy planning device, the planner observes the radiation planning fluoroscopy image on the screen of the image display monitor and decides the radiation area. When the planner has decided on a radiation area, X ray film shooting is conducted, and the radiation area is indicated by, for example, drawing a line showing the radiation area on the X ray film, and the planning for the therapy is completed.
The X ray film created by the radiation therapy planning device is sent to the operator of the radiation device. The operator of the radiation device will refer to the X ray film in which the radiation area is indicated and conduct treatment by external radiation of the relevant region (malignant tumor and the like) of subject M.